OCI8 Fast Application Notification (FAN) Support

FAN support gives fast connection failover, an Oracle Database high availability
feature. This allows PHP OCI8 scripts to be notified when a
database machine or database instance becomes unavailable. Without
FAN, OCI8 can hang until a TCP timeout occurs and an error is
returned, which might be several minutes. Enabling FAN in OCI8 can
allow applications to detect errors and re-connect to an available
database instance without the web user being aware of an outage.

FAN support is available when the Oracle client libraries that PHP
links with and the Oracle Database are either version 10gR2 or later.

FAN benefits users of Oracle's clustering technology (RAC) because
connections to surviving database instances can be immediately
made. Users of Oracle's Data Guard with a broker will see the FAN
events generated when the standby database goes online. Standalone
databases will send FAN events when the database restarts.

For active connections, when a machine or database instance becomes
unavailable, a connection failure error will be returned by the
OCI8 extension function currently being called. On a subsequent
PHP script re-connect, a connection to a surviving database
instance will be established. The OCI8 extension also
transparently cleans up any idle connections affected by a database
machine or instance failure so PHP connect calls will establish a
fresh connection without the script being aware of any service
disruption.

When oci8.events
is On, it is suggested to
set oci8.ping_interval
to -1 to disable pinging, since enabling FAN events provide
pro-active connection management of idle connections made invalid
by a service disruption.

To enable FAN support in PHP OCI8, build PHP OCI8 with Oracle 10gR2 or later
libraries and then follow these steps:

As a privileged database administrator, use a program like
SQL*Plus to enable the database service to post FAN events, for
example: